Scientists have confirmed that an asteroid previously targeted in a NASA planetary defence experiment has had its solar orbit slightly altered. The achievement marks the first time that humans have deliberately changed the orbit of a celestial body around the Sun. Researchers say the result could provide valuable insight for future efforts aimed at deflecting potentially hazardous asteroids.
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The experiment involved NASA’s Double Asteroid Redirection Test (DART), launched in 2021. In 2022, the spacecraft intentionally collided with Dimorphos, a small asteroid that orbits a larger body known as Didymos. The system was selected specifically because it posed no risk to Earth. Early observations confirmed that the impact shortened Dimorphos’s orbit around Didymos, but scientists have now verified that the collision also slightly changed the pair’s orbit around the Sun.
According to findings published in Science Advances, the change was extremely small. The asteroids’ solar orbit, which takes around 769 days to complete, was shortened by roughly 0.15 seconds and reduced by around 720 metres over a journey of hundreds of millions of miles. Researchers emphasised that even such minor deflections can become significant over decades, potentially making the difference between an asteroid striking Earth or passing safely by.
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Scientists believe that debris ejected from the impact, including millions of kilograms of rock and dust, contributed additional momentum to the deflection. Further insights are expected when the European Space Agency’s Hera spacecraft reaches the asteroid system in November. Unlike DART, Hera will not collide with the asteroids but will conduct detailed surveys and deploy small probes to study the aftermath of the impact.
